Organic winter wheat isn't supposed to yield 100 bushels per acre, but it did at Bozeman in 2007.

Scientists are still trying to figure out how a plot of organic winter wheat at the Post Research Farm west of Bozeman hit the 101 bushels per acre mark. Nearby organic test plots were almost as good, yielding "in the high 90s," said Perry Miller, Montana State University cropping systems researcher.

The precedent-setting harvest was on a plot that had been managed organically for four years prior to the 2007 winter wheat crop. The system used winter peas in the year preceding winter wheat planting. Winter peas accumulate nitrogen from the air and "fix" it in nodules on their roots. The peas were used in place of commercial fertilizer. When a crop is used this way, it is called "green manure."

"I still can't fully explain where all the yield came from," Miller said. "I thought we might have a 70-bushel-per-acre crop. The first inkling that it would be a big yielder was when we started combining and realized that we needed to get bigger sample bags. The timing of moisture must have been near perfect, because in July we had only a tenth of an inch of rain and 100-year record-breaking heat, too."

The yield came with Yellowstone hard red winter wheat, developed at MSU by Montana Agricultural Experiment Station winter wheat breeder Phil Bruckner. Conventionally fertilized plots of Yellowstone at the same research farm yielded 121 bushels per acre.

Though yield sometimes comes at the expense of protein in organic wheat, all of the winter wheat plots at Bozeman yielded better than 12.5 percent protein in 2007.

On an organic trial at big Sandy on Bob Quinn's farm, moisture, protein and yields were lower in 2007 than at Bozeman.

"Protein has been an issue in both years of a related study at Big Sandy," Miller said. "There, we have consistently fallen short on protein even with our best green manure practices." Protein levels in Big Sandy have run between 8.5 percent and 10.5 percent.

Miller said his most optimistic computer projections for the Bozeman plots project just 80 bushels per acre, and his inability to explain the excellent grain yield and quality concerns him.

"With my inability to explain the yield, I've been trying to figure out what we've really learned from the study," Miller said.

One side of the story is that the high 2007 organic winter wheat yields prove that it is possible to grow very high-yielding wheat organically, he said. In addition, some of the highest yields were obtained where researchers did not till the winter pea manure into the ground but roller-crimped it.

"In our long term rotation study, organic wheat yielded equal or greater than well fertilized no-till winter wheat during the first four years, and frequently had superior grain quality, with consistently heavy test weights, while no-till frequently failed to make No.1 grade standard due to light test weights."

On the other side of the story, Miller said organic wheat production may be less predictable, and risk seemed to increase with time. Soil phosphorus levels are declining rapidly in Bozeman, as are other nutrients.

In the fifth and seventh years of a long-term crop rotation study at Bozeman, the organic winter wheat crop failed both times. The failure in 2005 was due to an unusually dry fall that led to poor fall establishment of winter wheat and unacceptable weed competition and in 2007 due to stripe rust infection, compared with excellent yields from conventional no-till.

In both cases, Miller said that commercially available pesticides could have effectively saved the crop but would have meant stepping out of organic production. The long-term crop rotation study will be in its ninth year in 2008 at Bozeman. The organic system has required a crop rotation change to attempt to compete more aggressively with Canada thistle, and Clain Jones, Extension Soil Fertility Specialist, is implementing some expensive one-time organic phosphate fertilizer treatments to see if that soil nutrient can be remedied.